The present invention is related to the general surgical repair of separated body tissues, and more particularly to internally fixating and stabilizing such body tissues, specifically bones.
In the present state of the art, there are a number of systems available to repair biological tissues separated in surgery or by injury. These products serve to approximate and stabilize the tissues so that healing may commence and provide compression in the interface to promote healing. Compression and stability are critical for proper anatomical healing of tissue. With the correct amount of compression applied to the interface of the tissue portions to be joined, signals are sent to the tissue, thus allowing the tissue to remodel in proper anatomical position. The amount of compression applied to the tissue interface needs to be appropriate to the type of tissue that is being healed.
Twisted wires are also typically used to keep bone fragments together so they may heal. Twisted wires only hold tension as long as the twisted wire pair remains stable. Often the wires untwist too soon, thus failing to keep the bone fragments together so that they may heal. Wires can also cut into the bone fragments, thereby allowing them to separate so that healing is difficult.
When it is necessary to access the thoracic cavity for a medical procedure, for example, it is required to cut the sternum into two pieces using a sternal saw. Once the procedure is completed within the thoracic cavity, the sternum must be repaired. For such repairs, it is known to use a dynamic compression device, such as the spring device A shown in FIG. 1. Some of the drawbacks of this typical device A, and others which are used include:
1. Bulky spring materials, while occupying substantial space, often do not store much energy. Some use polymer elastic bands, while other use coiled springs;
2. Wires are sometimes used to wrap the bones into position in compression with one another. However, wires can have sharp ends that can damage adjunctive tissues, and the wires can also cut into the bone, as mentioned above. Knot stacks in suture can interfere with the natural movement of surrounding tissues; and
3. Current banding systems that incorporate a biasing mechanism to achieve dynamic compression put the biasing mechanism in line with the band or suture. This practice competes with precious space at the healing site. Suture or bands are used to approximate tissues so that they may heal. It is desirable to obtain the best purchase possible on the tissue, so that the binding mechanics offered by the suture may be utilized. The best purchase is optimized by ensuring that the suture has the greatest contact area with the tissue. If a biasing mechanism is interfering with this concept, the biasing mechanism may diminish the suture's ability to hold the tissues together.
Bands are advantageous over wires for a number of reasons. A band, by definition, is wide. In being wide, a band distributes its forces over a wider surface area. This inhibits the band from digging into the bone, unlike wires. In being wide, a band affords a larger cross-sectional area whereby more material may be realized, thus presenting the opportunity to offer as much strength in the construct as is necessary to hold the bone fragments together. As such, bands address wires' two main weaknesses, namely, digging into the bone fragments being held together and, not having sufficient cross sectional area.
Bands have different attributes than wires, some of which are difficult to manage. With strength comes stiffness, as mentioned elsewhere herein. The larger cross-section of the band significantly increases the stiffness of the band. While stiffness and rigidity are good attributes in that they can stabilize the bone union, these attributes can also prevent the band from following the contours of the bone when inserted. This can lead to capturing tissues underneath the band that ultimately destabilize the union as the tissues continue to compress and disappear over time. Binding the band ends together can also impose some problems. Generally this involves a mechanism on one band end that interfaces with holes or slots or contours on the other band end. This creates a tensioning system that is incremental in nature. As in the twisted wire system, this mechanical interface of the two ends is the weakest link in the system. This mechanical interface becomes stronger as the incremental steps become larger. But larger incremental steps aren't conducive to fine tuning the tension, so this is problematic. Flat sutures have been used to tie tissues together but the residual tension supplied in such a knotted structure is insufficient for optimum healing. There is a lot of fuss/time associated with trying to keep and hold a desirable tension with these flat sutures. What is needed is an attachment means that provides variable tensioning. Another problem associated with all banding systems is that they tension by pulling asymmetrically to one side requiring constant re-centering while tensioning the band. What is needed therefore is a banding system with the ability to tension symmetrically without requiring re-centering of the band.
Buckles demonstrate many of the needed aspects of joining two strap ends together in surgery. However, what is needed is a buckle/strap system that has the ability to free one strap end from the buckle such that it can be attached to a needle, routed through tissue, simply detached from the needle, and then attached to the buckle.